Prior art systems for video enhancement of the edges of characters are generally of an analog nature. These analog devices usually have critically designed delay lines and other analog components. Further, such systems, while capable of providing video edge information, to a certain extent have the inherent limitation that they can not provide such information all around the character.
One approach for providing a digital all-around edge device is described in U.S. Pat. No. 3,918,039 to Clark. This device, however, is complicated in its use of 4 different clock phases and various shaping and phasing devices.